package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {
    @Autowired
    private StringRedisTemplate stringRedisTemplate;
    @Autowired
    private CacheClient cacheClient;

    @Override
    public Result queryById(Long id) {
        //缓存穿透
//        Shop shop = queryWithPassThrough(id);
        Shop shop = cacheClient
                .queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);

        //缓存击穿
//        Shop shop = queryWithMutex(id);
        if (shop == null) {
            return Result.fail("商铺不存在！");
        }
        return Result.ok(shop);
    }

    //缓存穿透模板
    public Shop queryWithPassThrough(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1、从redis查询商铺缓存
        String stringJson = stringRedisTemplate.opsForValue().get(key);

        //2、判断是否存在
        if(StrUtil.isNotBlank(stringJson)){
            //3、存在，直接返回
            return JSONUtil.toBean(stringJson, Shop.class);
        }
        if(stringJson != null){
            return null;
        }

        //4、不存在，根据id查询数据库
        Shop shop = getById(id);

        //5、不存在，返回错误
        if(shop == null){
            //将空值写入缓存
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }

        //6、存在，写入redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        //7、返回
        return shop;
    }

    //缓存击穿模板
    public Shop queryWithMutex(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1、从redis查询商铺缓存
        String stringJson = stringRedisTemplate.opsForValue().get(key);

        //2、判断是否存在
        if(StrUtil.isNotBlank(stringJson)){
            //3、存在，直接返回
            return JSONUtil.toBean(stringJson, Shop.class);
        }
        if(stringJson != null){
            return null;
        }
        String lockKey = null;
        Shop shop = null;

        try {
            //4、实现缓存重建
            //4、1 获取互斥锁
            lockKey = LOCK_SHOP_KEY + id;
            boolean flag = tryLock(lockKey);
            //4、2 判断是否获取成功
            //4、3 失败，则休眠重试
            if(!flag){
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            //4、4 成功，根据id查询数据库
            shop = getById(id);

            //5、不存在，返回错误
            if(shop == null){
                //将空值写入缓存
                stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }

            //6、存在，写入redis
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //7、释放锁
            unLock(lockKey);
        }

        //8、返回
        return shop;
    }

    //获取锁
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    //释放锁
    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }

    @Override
    @Transactional  //保持数据的原子性
    public Result updateShop(Shop shop) {
        String key = CACHE_SHOP_KEY + shop.getId();
        if(shop.getId() == null){
            return Result.fail("商铺id不能为空！");
        }
        //1、更新数据库
        updateById(shop);
        //2、删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + shop.getId());
        return Result.ok();
    }
}
